Displaying announcement on all Jenkins pages - jenkins

Question

Is there a simple way or a plugin to display any custom message on Jenkins pages for all users? I wanted to display important changes or actions directly on Jenkins instead of emailing everyone.
What I mean is to have configurable panel similar to "Jenkins is going to shut down" which I could display and possibly change color. I tried to find plugins for that but found nothing.

Answer 1

Ok, I'll answer my dummy question, maybe someone will look for it later.
There's a plugin for injecting code to page header and footer:
https://wiki.jenkins-ci.org/display/JENKINS/Page+Markup+Plugin
It's not as easy to find as it should be downloaded from creators' page (link in description).
Without an extra plugin: In my case it was simpler as it was enough to add system message (manage jenkins -> configure system -> system message).
You can add CSS to Jenkins\war\css\style.css and use it in system message. I reused "shutdown-msg" which is displayed when jenkins is going to shut down.
#shutdown-msg {
font-weight: bold;
color: white;
background-color: #ef2929;
text-align: center;
margin-left: 2em;
margin-right: 2em;
margin-bottom: 0.5em;
padding: 0.5em;
-moz-border-radius: 0.5em;
}
#yellow-msg {
font-weight: bold;
color: black;
background-color: #eded78;
text-align: center;
margin-left: 2em;
margin-right: 2em;
margin-bottom: 0.5em;
padding: 0.5em;
-moz-border-radius: 0.5em;
}
#green-msg {
font-weight: bold;
color: white;
background-color: #34ba51;
text-align: center;
margin-left: 2em;
margin-right: 2em;
margin-bottom: 0.5em;
padding: 0.5em;
-moz-border-radius: 0.5em;
}
#blue-msg {
font-weight: bold;
color: white;
background-color: #2d72d8;
text-align: center;
margin-left: 2em;
margin-right: 2em;
margin-bottom: 0.5em;
padding: 0.5em;
-moz-border-radius: 0.5em;
}
#grey-msg {
font-weight: bold;
color: white;
background-color: #6b7777;
text-align: center;
margin-left: 2em;
margin-right: 2em;
margin-bottom: 0.5em;
padding: 0.5em;
-moz-border-radius: 0.5em;
}
<div id="shutdown-msg">Red message</div>
<div id="green-msg">Green message</div>
<div id="yellow-msg">Yellow message</div>
<div id="blue-msg">Blue message</div>
<div id="grey-msg">Grey message</div>